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Abstract

Stellar clusters can be considered as the building blocks of galaxies. Studying how clusters form and evolve is crucial in understanding the evolution of their host galaxies. Young massive stellar clusters, in particular, play a key role in placing constraints on the physics of star formation and evolution. The stellar population inside these extremely massive objects spans the full range of stellar masses from very low mass brown dwarfs to the most massive stellar objects currently known. One of the most important tools to study stellar clusters are stellar evolutionary models, i.e. tracks and isochrones from which masses and ages can be derived. Resolved stellar populations in clusters can in turn be used to test and calibrate these theoretical models. In this work I first present a study of the current generation of pre-main sequence models and their thorough use for assessing stellar properties. I then continue using stellar models to study the most massive young cluster in the Milky Way: Westerlund 1. The last part of this work deals with the first multiple wavelength investigation of a recently discovered star forming region: the CN15/16/17 complex. This region was observed in the framework of an extended cluster search. I used near infrared observations to look for the missing cluster that are yet to be found in our Galaxy in order to unveil the mysteries of star formation in the inner parts of the Milky Way.